Electron-discharge apparatus



Sept. 25; 1923. A

H. E. DUNHAM ELECTRON DISCHARGE APPARATUS Filed March :23, 1921" p/a te Cur-rent Inventor:

Harry E. Du n h am,

y Ea His Attorney.

Patented Sept. 25, 1923.

A UNITED STATES PATENT OFFICE.

HARRY E. DUNHAM, OF SCHENECTADY, NEW YORK, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

ELECTRON-DISCHARGE APPARATUS.

Application filed March 23, 1921. Serial No. 454,829.

T 0 all whom. it may concern:

Be it known that I, I'IARRY E. DUNI-IAM,

a citizen of the United States, residing at device which I prefer to employ comprises Schenectady county of Schenectady, State of. New York, haveinvented certain new and useful Improvements in Electron-Discharge Apparatus, of which the followingis .a specification.

My present invention relates to electron discharge apparatus and more particularly to that type of apparatus the operation of which depends upon producing and varying the emission of secondary electrons from a cold electrode. I

One of the objects of my invention isto provide a simple and efficient means and method for operating a device of the type mentioned.

A more specific object of my invention is to provide a simple and eflicientapparatus Y and method for receiving (Ol'ltlllllOllS wave signals whereby an audible indication of desired signals which are normally incapable of giving such an indication may be ob tained. In attaining the more specific object of my invention I include in the circuit upon which signaling currents to be detected are impressed, an :electron discharge device sothat the signaling current flowing in the circuit. is carried through. this deviceby means of electrons. By varying the number of electrons which can'fiow between the electrodes of this device the resistance of the circuit maybe varied in any manner desired. In the present case I prefer'to vary the number of electrons flowing by means of an electrostatic field produced upon a grid electrode which is properly positioned to vary the flow of electrons. If the'potential of this grid electrode .is varied periodi: cally between certain positive andnegative values at a frequency somewhat different from that oft-he signaling currents to be .detee-ted. the resistance of the signaling circuit wil be varied periodically between maximum and minimum values and the current in the circuit may be caused tovary at an audible frequency. I also preferably arrange the electron discharge device in such a way as to produce a negative resistance between the cathode andthe controlling grid. By tuning the circuit between the cathode and controlling grid oscillations will be produc'ed in that circuit and the potential of the grid will automatically be caused to vary grid.

the third electrode.

periodically at the frequency of the oscillations produced.

The'specilic form of electron discharge an electron emitting cathode, an anode, a third e'ectrode and a discharge controlling A constant positive potential is impressed upon the anode and a smaller positive potential is impressed upon the third electrode. Ifthese potentials are properly chosen secondary electrons will be emitted from the third electrode which will be attracted by the anode. It has been customary in the past to operate devices of the type de scribed in such a. way that a negative resistanceis produced between the cathode and If under this condition of operation signals are impressed upon the circuit between the cathode and third electrode by'means of the usual tuned receiving circuit, the circuit hasa tendency to oscillate continuouslyat the signaling frequeney. 'To

overcome this tendency special means'must circuit be employed in which the current can flow in either direction. An inspection of the usual character1st1c curve of the device described shows that there are two points wherethis last condition may be fulfilled, the first point being where the resistance of the, circuit is negative and the potential 'of the third electrode is appreciably lower than that of the anode, and the especial-1y suitable point to use for carrying"- 0 out my invention and since the circuit has a positive resistance characteristic when operated with the potential of the third electrode chosen to fall at this point on the characteristic curve there is no tendency for the circuit to oscillate.

The novel f atures which I believe to be characteristic of my invention are set forth with particularity in the appended. claims.

My invention itself, however, both as to sents a set of characteristiccurves showing its organization and method of operation will best be understood by referenceto the following description taken in connectionwith the accompanying drawing in which Fig. 1 shows diagrammatically the preferred form of circuit arrangement for carrying my invention into efl'ecnand Fig. 2 reprethe relation between current in the signaling circuit and,the otential impressed upon that circuit for difierent values of potential of the controlling grid.

As indicated in Fig. 1' of the drawing, I

utilize an electron discharge device 1 which comprises an electron emitting cathode 2, an

' anode 3, a third electrode 4 and a discharge controlling grid 5. The battery 6 whLch is connected in circuit between cathode and anode furnishes-the operatingpotential for the anode. The secondbattery 7, which is connected in the circuit between cathode and third'electrode furnishes the normal operating potential for the third electrode. 'A

third battery 8 connected in the circuit between cathode and discharge controlling grid' furnishes the normal. 0 crating potential for the grid. These p tentlals are so chosen that the circuit between cathode and discharge controlling grid willhave a negative resistance by reason of the emission of secondary electrons from the grid 5,

which. flow tothe anode 3. The potential of the battery 7 is also so chosen that secondary electrons will be emitted from the third electrode 4, which will flow to the anode 3, but in this case the potential'is chosen to fall a on or close to the point A on the characteristic curves of Fig. 2 instead of the point B, as has been customary in previous circuit arrangements in which devices of the type described have been employed. Signalmg potentials received 'upon the antenna 9 are impressed upon the secondary' of the trans former 10, which is included in'the external circuit between cathode and third electrode. This circuit may be tuned to the signaling frequency by means of the usual 'variable condenser 11. "Inductance 12 and capacity .13 are included in the circuit between cathode and grid 5-for tuning this circuit to a frequency slightly different. from that of the signaling frequency. Inasmuch as thiscircuit has a negative resistance characteristic oscillations will bep'roduced therein and the potential of the grid 5 consequently will be varied at a frequencv corresponding to the frequency of the oscillations produced.-

'The operation of the device will best be understoodby reference to the curves of Fig.

2 which show the relation between plate potential and plate current for different values of potential of the grid 5. The curve C represents the current for a high positive potential of the grid .5 and the curve E for a low or negative potential of'theg'rid 5. It-will be apparent from an inspection of these curves that'the effect of varying the grid potental'isto produce avariation in the apparent resistance of'the circuit between cathode and third electrode. In the normal operation of the system, the potential of the battery 7 being chosen to correspond to the voltage A at which the current flowing between cathode and third electrode is zero,

as long as the potential remains at this point the variation in the potential of the grid 5 will produce no changes-in the current flowing into the circuit between cathode and third electrode. If, however, a signaling po-' tential is .impressed upon the secondary of transformer 10 so that the total potential of the electrode 4 corresponds for example 'to the voltage F, a variation in the potential of the grid will vary the apparent resistance of this circuit between cathode and third electrode between a substantially infinite value a't-which the current is zero, and a much lower value at which the current is repre-' sented by the value G on the characteristic curve C; If the oscillations produced in the circuit of the-grid 5 were of the same frequency as the signaling current and properly phased with respect thereto, signaling potentialsof one sign would produce current between cathode and third electrode while signaling potentials of the opposite sign would produce no current in that circuit. The device then would in effect operate as a half .wave rectifier to produce a unidirectional current between cathode and third electrode.

If on the other hand currents produced in the grid circuit were of slightly different frequency from the signaling current, the current produced in the circuit between cathode 2ar1d third electrode 4 would consist of a number of current impulses in one direction followed by a number of current impulses -in the opposite direction as the phase relations changed and a current would beproduced in the telephone receiver 14: having an audible frequency component capable of affecting thelVhat I' claim as new and desire to secure by Letters Patent of the United States,is,

1-. Means for detecting high frequencysig paling currents comprising an electron discharge device having an electron emitting cathode. an anode. and a third electrode, means for impressing a constant positive potential upon the anode and means for impressing a smaller positive potential upon the third electrode, the potentials of said electrodes being so -choscn that secondary electrons will be given off from the third electrode and the normal operating potential of the third electrode being-of sucha value that an increase thereof will cause a decrease in the number of secondary electrons which will begivcn otf from the third electrode.

2. Means for detecting high frequency signaling currents comprising an electron discharge device having an electrom emitting cathode, an anode and'a third electrode, means for impressing a constant positive potential upon the anode,- means for impressing a smaller positive potentialupon the third electrode. the potentials of said electrodes being so chosen that secondary elec trons will be given ofi' from the third electrode and the potential of the third electrode being of such a value that an increasethereof will cause a decrease in the number of seconda'ry electrons which will be given off in accordance with the signals to be detected.

. 3. The combination in a signal receiving system of an electron discharge device having an electron emitting cathode, an anode, a third electrode and a discharge controlling member, means for producing an emission of secondary electrons from the third electrode, the potential of said third electrode being of such a value that an increase thereof wi l produce a decrease in the number, of secondary electrons which will be given off, means for varying the potential of thethird clectrode in accordance with the signals to be received. and means for varying the potential oi the discharge mm rolling member at a frequency which is independent of the frequeii -y of the signals.

4. The combination in a signal receiving system of an electron discharge device having an electron emitting cathode. an anode, a third electrode and a discharge controlling member. means for producing an emission of secondary electrons from the third electrode, the potential of said thirdelez-trode being of such a value that an increase thereot'will produce a decrease in the number oi secondary electrons which will be given off, means for varying the potential of the third electrode in accordance with the signals to be received, means for producing an emission of secondaryelectrons ,from the discharge controlling member sufficient to produce a tuned for a frequency different. from that of i the si nals to be received.

5. 'fhe method of operating an electron discharge device co nprising'an electron emitting cathode, ananodeand a thirdvelecnode, which consists in applying a constant 'iositive potential to the anode, applying to the third electrode a positive potential of such a value, 'as to causesecondary electrons to be given off from the third electrode and that the number of secondary electrons givenofl will decreaseif the. otential of the third electrode is increased, and .varying the potential'of the third electrode in ac- (ordance with'signals.

6. The'inethod of operating an electron discharge device comprisingan electron emittingcathode, ananodc a third electrode and a discharge controlling i'nember to detect high frequencysignals which consistsin applying a constant positive potential to.t'h e anode, applying to the third electrode fa positive'potential of, such a valueas to cause'secondaryjelectrons to be given off from the third electrode, and that the number of secondary electrons given bfi' will de crease if the potential of the third electrode is increased, varying the potential of the third electrode in accordance with the 'signalsto be detected, and varying the potential of the discharge-controlling member at a frequency which i sindependent ofthe signaling' frequency. t

7. The .methodof' operating an electron discharge device comprising an electron emittingcathode, an anode, a third electrode and a discharge controlling member to detect high frequency signals which consists in applying aconstant" positive potential to.

the anode, applying to the third electrode a positive potential of such a value as to cause secondary electrons to be given off from the third electrode, and that the nu'mher of secondary electrons given off will decrease if the potentialof the third electrode is increased, ,'varying the potential of the third electrode .in accordance with the signa s to 'be detected, producing an emission of secondary electrons fromthe discharge (ontrolling member sufficient to give the device a negative resistance characteristic be tween cathode and dischargecontrolling inembcn'producing oscillations bv means of said device and applying the oscillations thus produced to the discharge controlling member. a

S. The method of operating an electron discharge device comprising an electron emitting cathode, an anode, a third electrode and a discharge controlling member to detcct high frequency signals which consists in applying a constant positive potential to the anode, applying to the third electrode a positive potential of. such. a value as to cause secondary electrons to be given 011 from the third electrode and that the number of secondary electrons given off will decrease if-th potential of the third clectro de eat-bode and discharge controlling member .and periodically varying the potential of the discharge controlling member at a frequency slightly difilerentjrom that of the signals 10 .to be detected. r

- In witness whereof, I have hereuntoset I my hand-this 22nd (19. of March, 1921; HAB, Y E.DUNHAM. 

